1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to an image sensor with an anti-reflection film for preventing color crosstalk and a smear phenomenon and a method of manufacturing the same.
2. Description of the Related Art
An image sensor is a device which converts optical energy transmitted through each of red, green, and blue color filters into an electrical signal by using a photo diode and outputs the converted electrical signal by using a metal oxide semiconductor (MOS) transistor.
FIG. 1 shows a conventional image sensor.
Light transmitted through a micro lens 160 and each of red, green, and blue color filters 170, 171, and 172 reflects from a silicon surface and has a path {circle around (1)} or {circle around (2)} so as to reflect again from an adjacent photodiode 120, so that the light and a light having a path {circle around (3)} generate crosstalk. In addition, light having a path {circle around (4)} is mixed with an electrical signal of a photo diode, so that noises may occur.
Namely, the conventional image sensor has a problem in that light transmitted through a color filter may not be incident perpendicularly on a photodiode disposed below the color filter and may reflect from a metal wire line and be incident on an adjacent photodiode with light transmitted through an adjacent color filter.
In addition, light reflecting from the silicon surface may reflect again from the metal wire line disposed above the silicon surface and be incident on an adjacent photodiode, so that color crosstalk may be generated. In addition, the light may be incident on a transmitting pathway of an adjacent MOS transistor for transmitting a carrier generated from the photodiode and may generate an added carrier, so that the added carrier may be mixed with an electrical signal of a photodiode and cause noises.
In order to solve the aforementioned problem, a reflection film is formed in an interlayer insulating layer such that light reflecting from a silicon surface of a photodiode reflects from an upper reflection film and is incident on the photodiode in order to improve a light sensitivity.
FIG. 2 shows a conventional image sensor having a reflection film.
A reflection film 150 is formed between a photodiode 120 and a metal wiring layer. Therefore, light having the path {circle around (1)} transmitted through the micro lens 160 and the color filter 170, 171, or 172 reflects from a silicon surface and reflects again from the reflection film 150 so as to be incident on the photodiode, so that light efficiency increases.
However, light having the path {circle around (2)} reflecting from the silicon surface may not reflect from the reflection film 150 and reflect from a metal wire line 140 so as to be incident on an adjacent photodiode 120, so that the light and light having the path {circle around (3)} may generate crosstalk. In addition, light having the path {circle around (4)} may be mixed with an electrical signal of a photodiode, so that noises may occur.
In addition, since the reflection film 150 covers a portion of the photodiode 120, an effective region of the photodiode 120 is reduced. Therefore, when light is not in focus like light having a path {circle around (5)}, sensitivity may decrease